1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive comprising an inertial actuator latch with strip-spring biasing.
2. Description of the Prior Art
A computer system usually includes one or more disk drives for economical, non-volatile data storage. Prior art disk drives typically comprise a base for housing a disk and a head attached to a distal end of an actuator arm. A spindle motor rotates the disk about its axis, and a voice coil motor (VCM) rotates the actuator arm about a pivot in order to position the head radially over the disk. A crash stop is provided which facilitates latching the head in a park position while the disk drive is powered down in order to protect the data recorded on the disk as well as prevent damage to the head. The head may be parked on a landing zone on the inner diameter (ID) of the disk, or alternatively, the head may be parked on a ramp located at the periphery of the disk (a.k.a., ramp loading/unloading).
The actuator arm comprises a tang attached to a base end and positioned between a first arm and second arm of the crash stop. The second arm presents a physical barrier to the tang so as to limit the stroke of the actuator arm, thereby preventing the head from exceeding a radial limit (e.g., the edge of the disk). The first arm comprises a parking latch with a magnet for latching the tang to the first arm, thereby safely parking the head (e.g., on the inner diameter of the disk). In order to prevent damaging the head as well as the surface of the disk, the force from the magnetic parking latch helps prevent the actuator arm from unlatching when the disk drive is subjected to an external, physical shock. However, the actuator arm will unlatch if the physical shock is of sufficient magnitude, particularly if the physical shock causes the disk drive to rotate such that the magnetic parking latch is jerked away from the tang.
In prior art disk drives an inertial latch has been employed which prevents the actuator arm from unlatching when the disk drive is subjected to large rotational shocks. The inertial latch comprises a protruding arm which rotates about a pivot and xe2x80x9ccatchesxe2x80x9d the actuator arm to prevent it from unlatching during a rotational shock. The inertial latch also comprises a biasing mechanism for applying a biasing force to the arm in order to reposition it when the rotational shock subsides. Prior art inertial latches employ a torsion spring comprised of a wound coil which provides resistance to torque, thereby providing the biasing force against the rotation of the arm. However, torsion springs are complicated and expensive to manufacture, and their spring characteristics (e.g., spring constant) are sensitive to dimensional tolerances. Further, installing the torsion spring is difficult and requires a high degree of accuracy which further increases the cost and manufacturing complexity of the inertial latch.
Another problem with prior art torsion springs is the linear relationship between the displacement of the spring versus the load as illustrated in FIG. 6A. Because the relationship is substantially linear, it is difficult to design the torsion spring so that the inertial latch operates properly when the disk drive is subjected to small rotational shocks. Thus, the magnetic parking latch within the crash stop is typically designed to withstand larger rotational shocks than would be necessary if the spring load curve of the inertial latch were more constant. Designing the magnetic parking latch with a higher latching force to compensate for the insensitivity of a torsion spring further increases the cost of the disk drive.
There is, therefore, a need for a disk drive employing an improved inertial latch that is more cost-effective to manufacture and install, and more sensitive to small physical shocks.
The present invention may be regarded as a disk drive comprising a disk, an actuator arm, a head attached to a distal end of the actuator arm, a voice coil motor for rotating the actuator arm to position the head radially over the disk, a parking latch for latching the actuator arm in a latched position in order to park the head during a non-operating mode, a post, and an inertial latch for maintaining the actuator arm in the latched position when the disk drive is subjected to a physical shock. The inertial latch comprises a body having a protruding arm, a pivot surface, and a strip-spring comprising a first end inserted into a first receptor and a second end inserted into a second receptor such that the strip spring has an initial arc displacement when installed into the body. During the physical shock the body rotates about the pivot surface causing the protruding arm to engage the actuator arm and the strip-spring to press against the post to generate a biasing force. When the physical shock subsides, the biasing force rotates the body about the pivot surface to disengage the protruding arm from the actuator arm.
The strip-spring comprises any suitable shape, such as a substantially rectangular or cylindrical strip, and comprises any suitable material. In one embodiment, the strip-spring comprises a plastic film, and in another embodiment the initial arc displacement generates a restraining force for restraining the strip-spring within the inertial latch. In yet another embodiment, a dimension of the strip-spring (e.g., a length, width or thickness) is selected relative to a spring characteristic of the strip-spring.
The present invention may also be regarded as a method of manufacturing an inertial latch for use in a disk drive comprising a disk, an actuator arm, a head attached to a distal end of the actuator arm, and a voice coil motor for rotating the actuator arm to position the head radially over the disk. The method comprises the steps of providing a strip-spring comprising a first end and a second end and forming a body comprising a protruding arm, and a pivot surface about which the body rotates to engage the protruding arm with the actuator arm during a physical shock. The body is formed with a first receptor for receiving the first end of the strip-spring and a second receptor for receiving the second end of the strip-spring. The method further comprises the step of pushing the strip-spring into the first and second receptors such that the strip-spring comprises an initial arc displacement.
The present invention may also be regarded as an inertial latch for use in a disk drive, the disk drive comprising a disk, an actuator arm, a head attached to a distal end of the actuator arm, and a voice coil motor for rotating the actuator arm to position the head radially over the disk. The inertial latch comprises a strip-spring comprising a first end and a second end, and a body comprising a protruding arm and a pivot surface about which the body rotates to engage the protruding arm with the actuator arm during a physical shock. The body further comprises a first receptor for receiving the first end of the strip-spring and a second receptor for receiving the second end of the strip-spring, wherein the strip-spring has an initial, arc displacement when installed into the inertial latch.